Particularly in view of the backlash of increased energy costs resulting in a concentrated education process in recent years that dwellings should be well insulated with air leakages sealed about fireplaces, doors, windows, electrical wiring, keyholes, etc., it has not been uncommon to encounter asphyxia after expenditure of available oxygen within such dwellings to unsafe levels. This trend is even more pronounced in special housing conditions. Thus, for row or townhouses, less external house exposure to outside air further reduces the natural air replacement flow. Similarly for windowless walls such as in air conditioned complexes or in partly underground housing less air turnover may cause acute problems. Thus, it would be desirable to provide a system to monitor the oxygen level and provide control or alarm signals before dangerously low oxygen levels are encountered. However, one of the problems with installation of such systems is the oxygen detection. There are not available in the art simple, reliable, inexpensive oxygen detectors which can be available for ready installation in dwellings for detection and control of dangerously low oxygen levels.
It is also desirable in these tightly sealed dwellings that prevent rapid replacement of fresh air, that alarms may be available for other stale air conditions such as foul odors that disturb the human comfort index, even though these may not be as dangerous as the reduced oxygen levels. There are in this respect both explicit and general odor detection instruments available.
Of particular importance in considering contaminated or unsafe air levels in dwellings is the presence of radon gas. The Environmental Protection Agency has reported widespread presence of radon gas at levels unsafe for human occupancy over wide areas of the United States.
W. C. White in U.S. Pat. No. 2,579,352--Dec. 18, 1951 discloses means for detection of specific gases, vapors, smokes and other impurities in the atmosphere, and problems encountered in using ionization type detectors for quantitative measurements without fatigue, etc., are discussed. Thus, a flow of cleaning pure gas is interrupted by a flow of impure gas to be measured. However, it is not feasible with such a system to measure continuously a dwelling that may slowly pass from an acceptable oxygen level to a dangerously low oxygen level, even if this were able to detect oxygen.
At this time, there are available many inexpensive, special purpose smoke detectors operable with ionization detection. For the purpose of detecting foul odors of at least some types, thus, acceptable inexpensive detectors are available.
In general, as set forth by L. N. Liebermann et al. in U.S. Pat. No. 3,460,125--Aug. 5, 1969, ionization detectors have in the past been confined to detection of gaseous impurities, and not levels of oxygen. This particular detector has the ability to detect gases which either raise or lower the breakdown potential of a given atmosphere to an electric spark discharge. Any such instrumentation that depends upon critical high voltage discharge conditions cannot be used quantitatively because of the many influencing factors such as temperature, humidity and various uncritical gaseous conditions. This is particularly so for measuring a small slowly deteriorating change between acceptable and intolerable percentages of a given impurity.
Conductivity of high voltage sparks is measured by R. M. Stuck, U.S. Pat. No. 4,090,308--May 23, 1978 to determine the amount of ionizable matter in air flow paths. This method could not be adapted to reliably detect rather small changes in oxygen concentration of air, even if the sparking were an acceptable condition and could be inexpensively controlled for long term reliable performance without servicing.
There are no known portable detectors that can be used in-situ in a dwelling to measure contaminated air levels that are unsafe for human occupancy. Nor are there known inexpensive portable detectors providing instantaneous readout that can indicate the presence of radon gas at unsafe levels.
It is therefore an objective of this invention to produce improved instrumentation that can reliably detect air quality and determine unsafe conditions for human occupancy with reduced oxygen percentages in air, other impurities of the foul smelling type and the presence of radon gas, thereby to provide reliable and accurate instrumentation for determining air quality in dwellings.
Another objective of this invention is to provide portable instrumentation for in-situ immediate measurement of air quality in dwellings.